If you thought that only nerds require ultrasonic sensors and transducers then you are wrong. The devices are meant to make work easier across all fields and if you care to think outside the box, no matter how simple a problem you might be having, an ultrasonic sensor might be the solution.Because the sensors do not depend on color to give accurate measurements, they can be used on colored items or places as well as the transparent ones. With the sensors, the distance is measured through a reflection off the object is in question and the color is not an important variable. In most cases, you will not be in a position to manipulate the objects you are working with which could be a problem if you were to use a measuring device that gives the reading depending on the color. Include ultrasonic sensors and transducers in your list and the problem will be solved quickly.
Just like you may not have control over color, it might be impossible to control the lighting too. The environment you are working in might be full of liquid matter and it is impossible to maintain lighting especially if the distance is significant. Lucky for you, ultrasonic sensors can work even in dark environments. You will not be too happy if you are using cameras or proximity sensors which depend on light. Ultrasonic devices can even measure distance in space making them versatile. When you think of all the cool things you can do with these sensors, you might think that they cost loads of money but it is not the case. Some are as cheap as 30 dollars and anyone should be able to afford that. Given that they are calibrated before they hit the store, you will be buying something that you can use immediately.
With a parallel surface, not many devices will be able to give you great accuracy in the distance and thickness but you can never go wrong with ultrasonic sensors and transducers. Because the environment the devices are being used at might be dusty, dirty or moist, they are built to withstand that so that you can work with them in all kinds of surroundings. This is not to mean you should let dirt build up in them. There are ultrasonic sensors and transducers which have advanced technology which allows them to self-clean.